(a) Field of the Invention
The invention relates to a photodynamic treatment for the selective destruction of malignant leukemic cells without affecting the normal cells and without causing systemic toxicity for the patient.
(b) Description of Prior Art
Cancers are uncontrolled cell proliferations that result from the accumulation of genetic changes in cells endowed with proliferative potential. After a variable latency period during which they are clinically silent, the malignant cells progress to aggressive invasive and metastatic stages with tumor formation, bleeding, susceptibility to infections, and widespread dissimination throughout the body.
Despite important advances in treatment, cancers still acount for 28% of death in Western countries. Treatment of cancer has relied mainly on surgery, chemotherapy, radiotherapy and more recently immunotherapy. Significant improvement in outcome has occured with the use of combined modalities, for a small number of cancers. However, for the most frequent types of cancers (lung, breast, colo-rectal and the leukemias) complete remission and cure has not been achieved. Therefore, the development of new approaches for treating cancer patients is critically needed particularly for those patients whose disease has progressed to a metastatic stage and are refractory to standard chemotherapy. To overcome resistance, autologous stem cell transplantation (AuSCT) has been employed in the treatment of a number of advanced forms of cancer. Because high-dose chemotherapy with or without total body irradiation can be applied prior to AuSCt, increased response rates have been observed when compared with standard chemotherapy. One important issue that needs to be stressed when using AuSCT relates to the risk of reinfusing residual tumor cells despite histologic remission. A variety of techniques have been developed that can deplete up to 10.sup.5 of tumor cells from the marrow. These techniques, including immunologic and pharmacologic purging, are not entirely satisfactory. One major consideration when purging bone marrows is to preserve the normal hemopoietic stem cell compartment so that normal hemopoiesis can rapidly become reestablished upon grafting. The potential of photodynamic therapy, in association with photosensitizing molecules capable of destroying malignant cells while sparing normal hemopoietic stem cells, to purge bone marrow in preparation for AuSCT has largely been unexplored. This issue has been investigated in depth for one type of neoplasm, chronic myeloid leukemia (CML), since AuSCT has the potential to cure the disease and highly sensitive molecular biologic techniques are currently available to determine the efficacy of the purging procedure. Application of photodynamic therapy for treating other forms of leukemias, lymphomas and metastatic solid tumors is a distinct possibility in view of the functionnal properties of the dyes molecules which were synthesized in accordance with the present invention and whose description appears below.
Chronic myeloid leukemia (CML) comprises 15% of the leukemias. It is a clonal pluripotent hemopoietic stem cell disorder characterized by deregulated proliferation of bone marrow progenitors and circulating terminally differentiated myeloid cells. If left untreated this disease is invariably fatal.
Genetic analysis on CML cells has identified a highly characteristic abnormality consisting of a balanced translocation involving chromosome 9 and 22 where part of the c-abl protooncogene on chromosome 9 is juxtaposed to the 5' end of the bcr-1 gene on chromosome 22, leading to the formation of a fusion gene, a chimeric transcript and a P210 bcr/abl protein with tyrosine kinase activity. CML cells harboring the translocation are known as Ph-1+ cells, whereas non-clonal, presumably normal but suppressed marrow cells are known as Ph-1 negative (Ph-1-) cells.
Treatment of CML patient aims at eradicating Ph-1+ cells and reestablishing non-clonal Ph-1-hemopoiesis. Conventional myelosuppressive therapy with hydroxyurea, busulfan, and more recently with interferon-alpha (IFN-alpha) and hemoharringtonine (HTT) have failed to provide prolonged or complete clinical and cytogenetic remissions (reviewed in Goldman J. M. (1994) Blood Reviews, 8: 21-29). To date only allogenic bone marrow transplantation (ABMT) in young patients (&lt;55 years) with human leukocyte antigen-compatible (HLA-compatible) sibblings donor marrow has been shown to be curative in over 50% of good risks patients. However, only a minority of patients (20%) is eligible for allogenic bone marrow transplantation because of the lack of suitably matched donors or because patients are deemed too old to withstand the procedure. Therefore, alternative strategies to treat CML had to be developed. One promising line of research that has produced exciting results consists of restoring Ph- hemopoiesis by grafting patient's own marrow or peripheral blood stem cells that were harvested in chronic phase prior to intensive chemotherapy and total body irradiation. This procedure, known as autologous stem cell transplantation (AuSCT) involves, no or some ex vivo marrow manipulations to purge residual malignant Ph+ leukemic cells. To achieve eradication of the Ph-1+ clone several approaches have been proposed including:
1) in vitro exposure of the graft to 4-perhydroxycyclophosphamide (4-HC) or to a more stable derivative Mafosfamide.TM. (Asta-Z 7557); PA1 2) in vitro selection by growth in long-term culture; PA1 3) positive selection of CD34+DR- non-clonal stem cells; and PA1 4) in vivo therapy with combinations of antileukemic agents or with interferon-alpha followed by transplant. PA1 i) preferential localization and uptake by the malignant cells; PA1 ii) upon application of appropriate light intensities, killing those cells which have accumulated and retained the photosensiting agents; PA1 iii) sparing of the normal hemopoietic stem cell compartment from the destructive effects of activated photosensitizers; and PA1 iv) potential utilization of photosensitizers for bone marrow purging of harvested marrow in preparation for autologous bone marrow transplantation. PA1 i) preferential localization and uptake by the malignant cells; PA1 ii) upon application of appropriate light intensities, killing those cells which have accumulated and retained the photosensitizing agents; PA1 iii) sparing of the normal hemopoietic stem cell compartment from the destructive effects of activated photosensitizers; and PA1 iv) potential utilization of photosensitizers for bone marrow purging of harvested marrow in preparation for autologous bone marrow transplantation.
However, the clinical relevance of these methods remains to be established.
There are many reports on the use of photodynamic therapy in the treatment of malignancies (Daniell M. D., Hill J. S. (1991) Aust. N. Z. J. Surg., 61: 340-348). The method has been applied for cancers of various origins and more recently for the eradication of viruses and pathogens (Raab O. (1900) Infusoria Z. Biol., 39: 524).
The initial experiments on the use photodynamic therapy for cancer treatment using various naturally occuring or synthetically produced photoactivable substances were published early this century (Jesionek A., Tappeiner V. H. (1903) Muench Med Wochneshr, 47: 2042; Hausman W. (1911) Biochem. Z., 30: 276). In the 40's and 60's, a variety of tumor types were subjected to photodynamic therapy both in vitro and in vivo (Kessel, David (1990) Photodynamic Therapy of neoplastic disease, Vol. I, II, CRC Press. David Kessel, Ed. ISBN 0-8493-5816-7 (v. 1), ISBN 0-8493-5817-5 (v. 2)). Dougherty et al. and others, in the 70's and 80's, systematically explored the potential of oncologic application of photodynamic therapy (Dougherty T. J. (1974) J. Natl Cancer Inst., 51: 1333-1336; Dougherty T. J. et al. (1975) J. Natl Cancer Inst., 55: 115-121; Dougherty T. J. et al. (1978) Cancer Res., 38: 2628-2635; Dougherty T. J. (1984) Urol. Suppl., 23: 61; Dougherty T. J. (1987) Photochem. Photobiol., 45: 874-889).